1. Field of the Invention
The present invention relates to a magnetic tape cartridge or cassette having a resilient belt driving means and having separate tape and belt idlers. A magnetic tape cartridge is commonly referred to as a "cassette" and these terms as used herein are intended to mean the same thing.
2. Description of the Prior Art
Typical tape cartridges utilize tape which is 0.156 inches wide. Such tape is capable of storing only a limited amount of information. Recent tape recorders have been developed which require a tape cartridge which is capable of storing a much larger amount of information, as much as 120,000 bits per inch. To store this large amount of information, it has been proposed to use tape as wide as a quarter of an inch.
Recent video cassette recorders also require that the tape be transported at a relatively fast rate so that the desired amount of information can be adequately recorded and played back. Typical digital recording tape is generally 60 feet long and could provide 15 minutes of playing time. However, recent video recorders require as much as 300 feet of tape in order to provide 20 minutes of playing time. If such a long tape is to be used in a small cartridge, the tape must be extremely thin so that the size of the supply and take-up reels can be kept reasonably small.
Problems have been encountered in constructing a cartridge capable of transporting such a wide and thin tape. The tape tends to bounce in the vertical direction as it is transported past the machine heads. Tape bounce causes errors in recording and reading the tape especially when high recording densities are being used.
Prior art cartridges have attempted to minimize tape bounce by utilizing a resilient belt which attempts to turn the periphery of the tape take-up reel at a faster rate than it turns the tape supply reel in order to exert and maintain tension in the tape. FIGS. 1 and 2 show two such prior art cartridges.
In FIG. 1, a resilient belt 8 is driven in the direction of arrows 30 by a roller 26 which is driven by a recording machine capstan 28. The belt 8 passes around a portion 34 of a supply reel 6, around idlers 22 and 16, and around a portion 32 of a take-up reel 4. The stretching of the belt causes it to try to turn the periphery of the take-up reel at a rate faster than the periphery of the supply reel which applies tension to the tape as it is transported past the machine heads 33. The prior art cartridge shown in FIG. 2 is similar to that shown in FIG. 1 except that a floating idler 40 is used to guide the belt instead of fixed dual idlers 16 and 22 shown in FIG. 1.
These prior art cartridges have been found to be inadequate when a wide thin tape is utilized. Specifically, the tension supplied to the tape is insufficient to reduce the tape bounce to the degree required when very high recording densities are applied to the tape.